The present invention is a unit including an electric motor with constant current and electronics for control of the motor. The electric motor unit proposed by this invention is particularly well suited for a motorized fan group of a motor vehicle.
The blockage of a rotor of an electric motor with constant current creates a strong increase in the current. On motors without electronics, this abrupt increase in current destroys the line fuse before the thermal elevation, the result of this increase and the disappearance of ventilation, damages the motor and, specifically, its tracks, its blades, or also the stripes of its connection plate, etc.
On the other hand, in the case of a motor unit incorporating an electronic control, the electronic control limits the current in the electric motor, which can prevent the destruction of the line fuse in the cases where this destruction would hardly be desirable, avoiding a too significant increase of the temperature to the level of the power components of the electric control and at the level of motor elements.
In order to compensate for this inconvenience, one must, once one detects the blockage of the rotor, control the power supply of the electric motor according to a functioning sequence of the type illustrated in FIG. 1, that is to say, according to a succession of cycles of opening and closing. The duration t1 and t2 of the opening and closing are achieved by means of electrical delays incorporated into a motor unit and are chosen in such a way to prevent a too significant thermal increase in the motor unit.
On the graph on FIG. 1 is represented the intensity of the current through the electric motor during this sequence of the power supply, as well as the evolution of the temperature. The beginning of the blockage of the rotor is indicated by the dotted lines.
Generally, the length of time t2 during which the power supply of the motor is cutoff is generally longer than the length of time t1 during which the motor is powered. It is also possible to definitively stop the control of the motor after a certain number of power and cutoff cycles t1 and t2.
The goal of the invention is to improve the protection against thermal increases of a blocked rotor of an electronic motor unit incorporating an electric controller.
To this end, the invention proposes an electric motor unit with continuous current containing a connection plate and a card that carries electronics for the control of the motor, the card containing the means of monitoring the current in order to detect the blockage of the motor""s rotor, characterized by the card and/or the plate carrying the means of defining a temperature sensor(s) and by the card also containing means that control the power supply of the motor and are linked to the means of defining a temperature sensor(s), so that to the means of current monitoring, the means of control cut the power supply of the motor when the blockage of the motor""s rotor is detected and a temperature measured by the temperature sensor achieves a higher value threshold and reestablishes the power supply of the motor when the temperature is at least reduced to a lower value threshold.